Samsung HP-S4253 - 2 Seconds to black

[OneOfEm]

Now that I've been successful on a few monitors, I thought I'd try to tackle something bigger. This plasma cuts to black after 2 seconds.

The only things I see are:

• 3 of the large black CapXon are very slightly bulged - all of the large caps are CapXon
• The majority of the caps are SAMXON
• Some are SAMWHA

Should I plan on replacing all caps on the power supply or on all four boards?

Any other suggestions before I start?

[PlainBill]

Re: Samsung HP-S4253 - 2 Seconds to black

Now that I've been successful on a few monitors, I thought I'd try to tackle something bigger. This plasma cuts to black after 2 seconds.

The only things I see are:

• 3 of the large black CapXon are very slightly bulged - all of the large caps are CapXon
• The majority of the caps are SAMXON
• Some are SAMWHA

Should I plan on replacing all caps on the power supply or on all four boards?

Any other suggestions before I start?

Yeah, keep at least one hand in your pocket. These sets pack a serious punch.

The bulges are a plastic disc on the top of the cap. Replace them only if the aluminum can beneath that disc is bulged.

I wouldn't bother replacing ANY caps until you have a reason to suspect them.

The last picture shows the main control board. I believe two cables link it to the power supply. Usually the connectors on one or both boards are labeled with the voltages each pin carries. Check those voltages. Also, somewhere on the back of the plasma panel will be a white label indicating all of vital voltages for the panel. Verify those voltages are present.

You didn't mention the failure details. Does the TV sound continue after the picture goes black? Is there a sound of a relay opening after the picture goes black?

PlainBill

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Cold, everything works for 4-6 seconds then the picture fades to black over about 1/4 second. No click. The sound stays on.

After it's warmer, it's right at 2 seconds and it fades quicker.

Two of the large CapXon caps feel like there's a hard bulge under the plastic disk. Would it hurt to take the plastic disk off to see for sure?

The two connectors test as the attached picture shows. The green circles were right at the listed values, the two red circles were slightly low, as indicated. I have a cheap multimeter (with a new battery), so they might mean nothing.

I'm also attaching pictures of a label (I hope it's the one you meant) as well as some markings on the power supply that look to be similar info. I found test points (?) marked Va and Vs, but haven't found anything else yet that matches anything on the label. I tested those two. Va=65, Vs=2.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Found them.

Vset = .2
Vscan = -5.6
Ve = 1.5

Va has another test point on the same board as the others and it tests 65 here, too.

[PlainBill]

Re: Samsung HP-S4253 - 2 Seconds to black

Found them.

Vset = .2
Vscan = -5.6
Ve = 1.5

Va has another test point on the same board as the others and it tests 65 here, too.

All right!!! Now the question is - is the power supply bad, or is one of the sustain boards overloading the supply?

Those voltages go to the sustain cards. The usual technique is to disconnect the power leads to one of the sustain cards (with power off!!!), then turn on the TV and check the voltages. Reconnect that card, disconnect the other, and repeat. If only one sustain card causes the problem, that card is at fault (probably the Y-Sustain). If the voltage is low with either card connected, it's the power supply.

PlainBill

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Yep. The Y-Sustain board is the culprit.

Need a better picture of it?

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

This is as good as it gets tonight.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

OK... I found the attached as part of the Samsung service manual. (If it were a direct link, I'd post it, but it's on a file-sharing site.)

I've checked the four fuses and they're all OK.

I don't really know how to check for a short on the other parts, so I'm off to find a tutorial...

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Q5020 and Q5021 don't exist on this board. I guess that manual covers a series of boards?

[PlainBill]

Re: Samsung HP-S4253 - 2 Seconds to black

Note that by the symptoms you have a component that behave normally at room temperature and breaks down when it heats up.

There are about 25 available on eBay (ignore the one with the picture of the X main). At $50 plus shipping, I'm not sure how long I would spend trying to identify the problem.

PlainBill

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Agreed. I just ordered one.

Thanks so much for your help again, Bill!

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Well...

I ordered a "known good" Y-sustain and installed it, and the symptoms are exactly the same as I had before.

I've checked all of the test points both with and without the "new" Y-sustain board, and the results are the same as with the old board.

One other note, when testing it this time, one time it stayed on long enough for me to see the screen clearly and even to get a picture. There are two vertical bands of static fuzziness on the screen. I'm attaching an image to try to show what it's doing. Before I just thought that those bands were just part of the powering on and off.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Just a little more information:

Back in post #6, I said the Y-sustain board was the culprit. Since Bill said, "probably the Y-Sustain," that was the first and only board I checked. The numbers looked good when it was disconnected, so I didn't try the same check on the X-sustain card (even though he also said, "If the voltage is low with either card connected, it's the power supply" - I missed that part).

I just did.

Below are the full test results that I should have done before:

Both boards connected:

• Va 65
• Vs 2.9
• Vsc -4.6
• Ve 1.5
• Vset -.1

Y-sustain disconnected:

• Va 65
• Vs 197
• Vsc -187
• Ve 111
• Vset 185

X-sustain disconnected:

• Va 65
• Vs 197
• Vsc -187
• Ve 111
• Vset 185

The results are exactly the same with either board disconnected. I guess I should have checked both last week.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

I should have also pried the plastic discs from the large capacitors that felt like they were bulging.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

This might be part of the problem...

[Scenic]

Re: Samsung HP-S4253 - 2 Seconds to black

there's a reason why a lot of people call them cRapxon..

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

Replaced the two caps and it's up and running.

I appreciate the assistance again, Bill.

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

I spoke too soon. I've been doing some Xbox360 stress testing and thought all was good.

Just now, it snapped like a string firecracker while it was turned off. Perhaps I should have replaced more than just the two bulging caps. Will open it up again in the morning...

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

I'm assuming that the problem is something on the "hot" part of the power supply (since it popped with the power off). Is that a fair guess?

There's nothing visible. However, when I check voltages, this is what I get:

........On Label.........Tested
Vs.........197..............442
Va..........65..............145
Vset......195..............415
Vsc......-185.................0
Ve.........110..............248


Where should I look next? Need a clearer picture of that part of the board?

[OneOfEm]

Re: Samsung HP-S4253 - 2 Seconds to black

More information:

The fuses are all OK. There are 4 diodes that show resistance both directions (see image).

I could handle replacing them, but...

• How do I identify what they are and what replacements I'd need?
• Is it likely that these diodes are just symptoms of a larger problem?